(1) Field of the Invention
This invention relates generally to electronic timepieces and, more particularly, to a timepiece which comprises an oscillator and a divider chain.
(2) Description of the Prior Art
It is known that in developing an integrated circuit the number of connecting pins should be a minimum. A circuit comprising an oscillator and a divider chain and generating polarised pulses for driving a step motor requires at least six pins under the condition that no pole of the quartz be connected to the power supply. On the other hand, these circuits must be tested after fabrication for ascertaining a faultless operation.
As an example, let us consider a timepiece whose motor receives a pulse every minute: for testing its circuit, its motor must make at least two steps, i.e. two polarised pulses must be waited for. Furthermore, it is not known in which state the divider is when switching on the circuit. In the worst case, one minute elapses before the motor makes its first step. Therefore, a test of such a circuit takes from two to three minutes.
In a production with 9 working hours a day only 9 .times. 20 = 180 circuits can be tested every day. This number evidently is not sufficient.
Of course, it is possible to test several circuits in parallel. If the planned daily production is 1000 pieces, 6 circuits must be tested simultaneously. But the equipment for multiple testing is expensive and often difficult to implement.
Another method for testing such circuits consists in applying a higher frequency than normal to the divider chain or to a part of this chain. This method requires an additional pin, which often cannot be provided because a housing with 7 pins is not standard. On the other hand, the pulse length of the driving pulses are also reduced by speeding up the cycle. Then it is difficult to measure the residual voltage of the output transistors and the pulse duration. Similar problems arise when testing circuits for watches with active or passive display.